Theoretical Study on the H-Atom Abstraction Reactions of Three Linear Pentanol Isomers + HȮ₂ Radical

In this study, high-level ab initio calculations were carried out to systematically investigate the hydrogen atom abstraction (HAA) reactions from three linear pentanol isomers by hydroperoxyl (HȮ₂) radical. Geometry optimization, frequency analysis, zero-point energy (ZPE) corrections, and 1D hindered rotor treatments for low-frequency torsional modes between heavy atoms were carried out at the M06-2X/6-311++G(d, p) level of theory. For single-point energy calculation, the QCISD(T)/CBS level of theory was used for species with T1 diagnostic values below 0.035, while the CASPT2/CBS level of theory was applied to channels with T1 diagnostic value of transition states was higher than 0.035. Rate constants in the temperature range 500–2000 K were calculated according to conventional transition state theory with asymmetric Eckart tunneling corrections. Rate rules were summarized in combination with the results from branched pentanol isomers. Thermochemical properties calculation for all species were performed by the composite methods of G3/G4/CBS-QB3/CBS-APNO. The calculated rate constants and thermochemical data were integrated into the mechanism and validated against the ignition delay times (IDT). The results will effectively promote the combustion kinetic model development for pentanol isomers oxidation.